I'm facing a similar situation with a rooster whose beak was pretty much chewed off. I've spoon fed him for three days, and now I'm going to see what happens. If he can eat enough to keep himself going, that's great. If he can't eat, we'll probably put him down before he starves to death. Quality of life is the criteria here. If chickens can't do what they need to do to be chickens, it's more merciful to let them go and pat yourself on the back for doing what you could to help. Good luck.